Process for production of 1,1,1-trifluoro-2,2-dichloroethane

ABSTRACT

A process for production of 1,1,1-trifluoro-2,2-dichloroethane comprising chlorination of 1,1,1-trifluoro-2-chloroethane with chlorine gas in the presence or absence of a metal salt as a catalyst.

This application is a continuation of copending application Ser. No.07/586,372, filed on Sep. 21, 1990, now U.S. Pat. No. 5,111,899, whichis a continuation of Ser. No. 07/349,176, filed on May 9, 1989, nowabandoned, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for the production of1,1,1-trifluoro-2,2-dichloroethane. Particularly, the present inventionrelates to a process for the 1,1,1-trifluoro-2,2-dichloroethanecomprising chlorination of 1,1,1-trifluoro-2-chloroethane with chlorinegas in the presence or absence of a metal salt as a catalyst.

2. Description of the Related Art

1,1,1-Trifluoro-2,2-dichloroethane is expected to replacetrichlorofluoromethane, since it does not decompose ozone in thestratosphere. Thus, it is desirable to develop an economical process forthe production of 1,1,1-trifluoro-2,2-dichloroethane.

Several processes for the production of1,1,1-trifluoro-2,2-dichloroethane have been already proposed. Forexample, Czechoslovakian Patent No. 136,735 and Japanese Patent KokaiPublication No. 222038/1983 describe a process comprising reduction of1,1,1-trifluoro-2,2,2-trichloroethane. Japanese Patent Publication No.27375/1986 describes a process comprising isomerization of1,1,2-trifluoro-1,2-dichloroethane. U.S. Pat. No. 3,755,477 describes aprocess comprising fluorination of ethylene tetrachloride. JapanesePatent Kokai Publication No. 82711/1978 describes a process comprisingphoto chlorination of 1,1,1-trifluoro-2-chloroethane. McBee describes aprocess comprising chlorination of 1,1,1-trifluoroethane in J. Ind. Eng.Chem., 39, 409, (1947).

However, from a point of view of the economical production, the aboveknown processes for the production of 1,1,1-trifluoro-2,2-dichloroethaneare not necessarily suitable since the yield and selectivity throughsuch processes are not sufficiently high.

McBee describes that 1,1,1-trifluoroethane, which is a compound which issimilar to a starting material for the production of1,1,1-trifluoro-2,2-dichloroethane, reacts at reaction temperature of485° C. with chlorine at molar ratio of 1:1. Under these conditions, theconversion of 1,1,1-trifluoroethane has been 50%. The product throughthis process contains 22.5% of 1,1,1-trifluoro-2,2-dichloroethane and41.8% of 1,1,1-trifluoro-2,2,2-trichloroethane. It is reported that,judging from the fact that the amounts of the compounds of which allhydrogen atoms are replaced with chlorine atoms have been increased, thechlorination rate increases, as the chlorination proceeds, or, as thenumber of hydrogen atoms replaced with chlorine atoms increases.

Accordingly, the above report indicates that the molar ratio of1,1,1-trifluoro-2,2,2-trichloroethane to1,1,1-trifluoro-2,2-dichloroethane is more than 1, that is,1,1,1-trifluoro-2,2,2-trichloroethane produced in always more than1,1,1-trifluoro-2,2-dichloroethane.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide acommercially advantageous process for the production of1,1,1-trifluoro-2,2-dichloroethane in which the problems described aboveare overcome.

According to the present invention, there is provided a process for theproduction of 1,1,1-trifluoro-2,2-dichloroethane which process compriseschlorination of 1,1,1-trifluoro-2-chloroethane with chlorine gas in thepresence or absence of a metal salt as a catalyst.

In the process of the present invention, the production ratio of1,1,1-trifluoro-2,2-dichloroethane to1,1,1-trifluoro-2,2,2-trichloroethane is about 1:0.3 at about 50%conversion of 1,1,1-trifluoro-2-chloroethane and such the highproduction ratio cannot be expected from the report of McBee.Accordingly, becomes possible to produce1,1,1-trifluoro-2,2-dichloroethane economically.

DETAILED DESCRIPTION OF THE INVENTION

1,1,1-Trifluoro-2-chloroethane, as a starting material in the presentprocess, can be easily produced by fluorination of trichloroethylenewith anhydrous hydrogen fluoride in a liquid or gas phase.

The chlorination of the present invention can proceed with highselectivity even in the absence of a catalyst. Further, when a metalsalt is used as the catalyst, higher selectivity can be achieved.

Such a metal salt when optionally used in the present process includes ametal fluoride such as CrF₃ and a metal chloride such as CuCl₂, NiCl₂and FeCl₂.

It is preferable to use a metal salt which is carried on, for example asupport, made of a metal oxide such as aluminum oxide or activatedcarbon. The most preferable catalyst includes NiCl₂, CuCl₂ and FeCl₂carried on a support made of aluminum fluoride. Further, the supportitself can be used as a catalyst, that is the support alone can be used,without the catalytic compound describe above, which also provides goodproduction.

Generally, any type of support can be used, and it is most preferable touse a spherical support or a pellet form support of a size within therange of from 1 to 8 mm, particularly from 2 to 4 mm.

Amount of the catalyst carried on the support is suitably selecteddepending on the reaction conditions, the desired conversion and so on.Generally, the molar ratio of the metal salt as the catalyst to themetal oxide as the support, is in the range of from 0.005 to 2,preferably from 0.01 to 1.0, for example, 0.03.

The reaction temperature of the chlorination of the present process isgenerally in the range of from 250° to 500° C., preferably from 350° to450° C., for example 400° C. The reaction is usually performed underatmospheric pressure, although the present chlorination can be performedunder pressure.

The molar ratio of chlorine gas to 1,1,1-trifluoro-2-chloroethane ispreferably controlled in the range of from 0.05 to 0.5, particularlyfrom 0.1 to 0.4 by taking into account the selectivity to1,1,1-trifluoro-2,2-dichloroethane.

The contact time between the catalyst and the reactants can be suitablyselected depending on the reaction conditions, especially the reactiontemperature. Generally, the contact time is preferably controlled in therange of from 0.5 to 30 seconds, particularly from 1 to 25 seconds.

In the present process, any type of reactor, for example a tube reactor,can be used as long as good contact between the catalyst and thereactants can be ensured.

In the process of the present invention, the reactor such as a tubereactor filled with the support carrying a catalyst is heated to apreselected temperature dependent on the reaction temperature, forexample, in an electrical furnace. Then, 1,1,1-trifluoro-2-chloroethaneand chlorine gas are supplied to the reactor to initiate thechlorination. The exit gas from the reactor is generally collected afterwater washing and drying steps.

In order to improve the conversion of 1,1,1-trifluoro-2-chloroethane, itis advantageous to recycle the unreacted 1,1,1-trifluoro-2-chloroethaneto the reactor which is recovered from the top of a purificationapparatus for purifying the produced gas.

When no catalyst is used in the present process, it is advantageous touse an inert packing such as Raschig ring from the view point ofachieving better mixing of the gas and better heat transfer.

The present invention will be hereinafter explained further in detail byfollowing examples.

EXAMPLE 1

A tube reactor made of Hastelloy C (20 mm in inner diameter, 400 mm inlength) was filled with 50 ml of spherical support particles (from 2 to4 mm in diameter) made of AlF₃ carrying CuCl₂ in the molar ratio of 0.03to AlF₃, and then heated to 370° C. in a nitrogen stream. After stoppingthe supply of nitrogen, 1,1,1-trifluoro-2-chloroethane and chlorine gaswere supplied to the reactor at the flow rate of 100 ml/min. and 50ml/min. (based on the standard conditions), respectively. The contacttime based on the average residence time was about 8.5 seconds.

The exit gas from the tube reactor was collected after the water washingand the drying steps, and then analyzed with a gas chromatography. Theconversion of 1,1,1-trifluoro-2-chloroethane was 45% and the selectivityto 1,1,1-trifluoro-2,2-dichloroethane was 75%.

EXAMPLES 2-4

Using the same apparatus as Example 1, the process of the presentinvention was carried out without a catalyst. In these examples,1,1,1-trifluoro-2-chloroethane was reacted with chlorine gas at thetemperature of 400° C. with the ratio of the flow rate thereof as shownin Table 1. The exit gas from the reactor was analyzed as in Example 1.

The results are also shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                     Example 2                                                                             Example 3 Example 4                                      ______________________________________                                        Flow rate of 1,1,1-                                                                          90 ml/min.                                                                              80 ml/min.                                                                              70 ml/min.                                 trifluoro-2-chloroethane                                                      Flow rate of chlorine gas                                                                    10 ml/min.                                                                              20 ml/min.                                                                              30 ml/min.                                 Conversion of 1,1,1-                                                                         10%       22%       40%                                        trifluoro-2-chloroethane                                                      Selectivity to 91%       86%       77%                                        1,1,1-trifluoro-2,2-                                                          dichloroethane                                                                ______________________________________                                    

EXAMPLES 5-9

Example 1 was repeated except that the metal salt shown in Table 2carried on the AlF₃ support particles in the molar ratio of 0.03 wasused and the reaction temperature was changed as shown in Table 2.

The results are also shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                   Exam- Exam-   Exam-   Exam- Exam-                                             ple 5 ple 6   ple 7   ple 8 ple 9                                  ______________________________________                                        Catalyst     FeCl.sub.2 /                                                                          FeCl.sub.2 /                                                                          NiCl.sub.2 /                                                                        NiCl.sub.2 /                                                                        --                                                AlF.sub.3                                                                             AlF.sub.3                                                                             AlF.sub.3                                                                           AlF.sub.3                                                                           AlF.sub.3                            Reaction temperature                                                                       330° C.                                                                        370° C.                                                                        330° C.                                                                      370° C.                                                                      450° C.                       Conversion of                                                                              32%     48%     26%   51%   79%                                  1,1,1-trifluoro-2-                                                            chloroethane                                                                  Selectivity to                                                                             82%     72%     83%   71%   45%                                  1,1,1-trifluoro-2,2-                                                          dichloroethane                                                                ______________________________________                                    

COMPARATIVE EXAMPLE

1,1,1-Trifluoro-2-chloroethane and chlorine gas were supplied to a glasstube reactor (30 mm in inner diameter, 200 mm in length) made of PyrexGlass® (commercially available from Corning Glass Works, U.S.) under theillumination of a high pressure mercury lamp of 100 wattages. Their flowrates were 100 ml/min. and 50 ml/min., respectively. The residence timein the reactor was about 60 seconds. The temperature in the reactor was30° C.

The produced gas discharged from the reactor was analyzed with the gaschromatography after water washing. The conversion of1,1,1-trifluoro-2-chloroethane was 5% and the selectivity to1,1,1-trifluoro-2,2-dichloroethane was 10%. The remainder of the productwas 1,1,1-trifluoro-2,2,2-trichloroethane.

What is claimed is:
 1. A non-catalytic thermal chlorination process forproduction of 1,1,1-trifluoro-2,2-dichloroethane comprising chlorinating1,1,1-trifluoro-2-chloroethane with chlorine gas, in which a molar ratioof chlorine gas to 1,1,1-trifluoro-2-chloroethane is in the range offrom 0.05 to 0.25 and a reaction temperature is in the range of from350° C. to 450° C.
 2. The process according to claim 1, in which nocatalyst is used, the molar ratio is in the range of from 0.05 to 0.2and the reaction temperature is 350° C. to 420° C.
 3. A thermalchlorination process for production of1,1,1-trifluoro-2,2-dichloroethane comprising chlorinating1,1,1-trifluoro-2-chloroethane with chlorine gas in the absence of acatalyst, in which a molar ratio of chlorine gas to1,1,1-trifluoro-2-chloroethane is in the range of from 0.05 to 0.4 and areaction temperature is in the range of from 350° C. to 450° C.
 4. Theprocess of claim 3, wherein said reaction temperature is about 400° C.